Obesity among children is one of the most pressing public health problems in the United States. We currently have few policy tools to effectively reduce obesity at the population level. However, schools are a prime place to influence this epidemic. The School Food program, including both the school lunch and breakfast programs, serves more than 30 million children every day, making it arguably one of the most important levers available to policymakers for improving the diet of America9s youth. Although the federal government provides funding assistance and strict dietary guidelines to these programs, their success is shaped critically by policies adopted by schools and school districts regarding price, menu, quality, variety, timing, context, method of delivery, means of payment, and available alternatives. Together these affect student participation in school meal programs, consumption of healthy foods, and, ultimately, childhood obesity. The New York City (NYC) public schools offer a unique laboratory for studying the effects of school food policies on program participation, obesity, and academic achievement. With its 1.1 million students and more than 1,600 schools, NYC exhibits wide variation in food policies and programs across schools, considerable diversity in neighborhood settings and contexts, and a remarkably diverse student body. NYC has also long been at the cutting edge in its efforts to combat youth obesity. For example, in 2005, the city schools began collecting annual FITNESSGRAM data on height, weight, body mass index (BMI), and indicators of health-related fitness for more than 200,000 students. In 2008, the program expanded to well over 750,000 students. In this project, we will link FITNESSGRAM data collected in NYC to individual student and school characteristics to better understand the influence schools have on student health through their food policies. Specifically, we seek to use econometric methods to investigate the role school and district food policies have on (a) BMI, (b) meal program participation, and (c) academic outcomes. The first outcome is available to us for individual students through the FITNESSGRAM, while meal program participation is reported by income group and school. Academic outcomes for individual students--linkable to the FITNESSGRAM--are available to us for the universe of students grades 1-12. Data on district policies, school practices, and neighborhood context will be collected via a city-wide survey of schools, interviews with district personnel, and several school case studies. This project will provide considerable data on the impact of a wide range of school food policies on childhood obesity, through direct observation of BMI. As other school districts and state and federal policymakers struggle with policy approaches to influence childhood obesity, these results will indicate which policies are successful and worth pursuing.